An electrolytically polymerizable macromolecular compound which is advantageously usable as a surface modifier for a polar surface, as a compatibilizing agent for polymer alloys, as an adhesive primer, as an electrochromic substance, etc., a polymerizable monomer to be used for the production thereof, and a method for the production of an electrolytically polymerized film thereof are disclosed. The macromolecular compound has a repeating unit represented by the following general formula (2): ##STR1## wherein R.sub.1 represents a hydrogen atom or an alkyl group, A represents an electrolytically polymerizable group, and B represents a divalent group. This macromolecular compound is obtained by the polymerization of a monomer represented by the following general formula (1): ##STR2##